Preparing compounds of chromium oxid.



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ERNST VOET'I'EE, UF KJREFELD, NEAR BOCK'UM, GERMANY.

PREPARING COMPOUNDS F CHROMIUM 0.73.11 3.

Ho Drawing.

To all whom it may concern.

Be it known that I, ERNST Vonrrnu, chemist, a subject of the King of Wurttemberg' and the German Emperor, residing at Boole umerplatz 2, Krefeld, near Bockum, Kingdom of Prussia, German Empire, have invented a new and useful Improvement in Preparing Compounds of Chromium Oxid;

and I do hereby declare the following .to be a -full, clear, and exact description of the same. I,

The conversion of chromic acid orchro mates into lower oxidation stages is commonly effected by the action of glucose in the presence of acids, whereupon astron reaction sets in and a chromium salt 0 the acid is obtained, 6. g. chromium sulfate;

These chromium solutions may be used either immediately or first neutralized with alkalis or salts of organic acids, as sodium acetate, or else solutions of hydrated chro- -mium oxid are formed by the action of sodium tit) hydrate solution. These chromium compounds are extensively used as tanning and mordanting agents.

it is now found that under certain conditions chromic acid and chromates can be reduced without an addition of acid, indeed even in an alkaline solution. In neutral solutions, insoluble hydrated chromium oxid is obtained in the form of black shining grains which dissolve readily in acid with the evolution of gas. In alkaline solution, soluble complexbasic chromium compounds are formed which may be converted into salts of any basicity by the addition of acids.

The water-insoluble hydrated chromium oxid found by me is produced by the action jot lucose on acid chromates and chromic aci in some cases with an addition of thiosuliate. When employing chromic acid, the reaction sets in with glucose without the aid of heat, but when employing acid dichromates and glucose the mixtures must be brought nearly to the boiling point. it, however, thiosulfate is added, the reaction takes place at a considerably lower temperature. The stable chromium compound thus produced is in the form of black shining grains. This body contains chromium hy- Specification of Letters Patent.

Patented June 2W1 '2.

Application filed July 2, 1914. Serial No. 848,561.

droxid, carbonic acid chemically combined, organic acids of the aliphatic series and aldehydesof the aliphatic series. An exact formula cannot be given for the compounds because the relative proportion of the components varies. The compound is particularly adapted for tanning purposes.

Furthermore, I' have found that when ,reducing chromates with glucose, for instance, in the presence of ammonla, z. ein a weakly alkahne solutlon, a water-msoluble monia may be partly replaced by sodium carbonate, and glucose likewise by thiosulfate.

It was then found that by reducing chromates with glucose or other sorts of sugar in a neutral or weakly caustic alkaline solution basic chromium carbonate in the soluble form results. The liquid obtained is green, thick, syrupy and readily soluble in water. It is a matter of surprise that acid may be added to the solution until it reacts perfectly neutral, without precipitation taking place, the solution remaining perfectly clear until a small excess of acid precipitates hydrated chromium oxid which,

with a further addition of acid, readily dissolves in the cold. In this way, normal or hydrated chromium oxid is obtained. Am-

more or less basic salts are obtained, which may be immediately employed for tanning and mordanting.

Theproduction is very simple. Either neutral chromate is used or chromic acid or dichromates are converted into the neutral, yellow salt by an addition of alkalis, as sodium hydrate solution or sodium carbonate, adding if necessary, a small excess of pounds being immediately fixed on said substances in the very moment of their formation.

According to the purpose for whichit is to be employed, thechromic acid may be only partially reduced, the result being a mixture of chromates and chromium salts.

Example.

1. Dissolve 82 kg. sodium dichromate in 78 1t. water, add 40 4:5 glucose solution and 22 kg. thiosulfate and warm 'to -80 6., at which temperature reaction sets in. Without any further introduction of heat, the temperature rises to 110 C. 1 Much gas evolves and a porous,

black-shining product is formed, which may be used immediately or cleansed by washing in water.

As an example for producing a solutlon therefrom, a mixture of 100 It. sulfuric acid 60 C. and

50 water is poured over 260, kg. of the crude product.

Solution takes place gradually with the evolution of much heat, and gas consisting chiefly of carbon dioxid mixed with small amounts of carbon monoxid; and the result is a highly concentrated chromium extract of 00 18., which may be used for tanning and mordanting, either immediately or after being neutralized with sodium carbonate or salts of inorganic acids, 6. g. sodium acetate.

After a short time, much gas is evolved, and black shining grains are formed, which may be used as stated in example No. 1.

3. Dissolve 82.0 kg. sodium dichromate in 08.0 It. water, add 48-50 sodium hydrate solution at 40 B. and then 80 1t. 1: 1 glucose solution.

When the mixture is brought to 80 (1, much gas is evolved, and the temperature increases. The reaction ceases after a short time, and the result is a bright green syruplike liquid which gives a ciear solution in cold water.

masses 4. Dissolve 89.4 kg. sodium chromate in 80.0 lt. water, add 40.0 4:5 glucose solution and finally 22.0 kg. thiosulfate.

When brought to about 80 C., a strong reaction sets in, and the result is a syruplike green liquid which readily dissolves in water.

5. Dissolve 55 kg. chromic acid in 06 1t. water and add gradually 40 1t. 4-:5 glucose solution. The temperature rises and gas is evolved, the ,result being a porous, black-shining product.

The above-stated quantities'may be altered according to requirements.

l claim as my invention 1. Process of preparing organic chromium compounds especially well adapted for tanning purposes, which consists in reducing compounds containing chromic acid with sugars in the absence of free acid other than chromic acid.

2. Process of preparing organic compounds of chromium oxid, which consists in reducing dichromates with sugars in the absence'of free acid.

3. Process of preparing organic chromium compounds which consists in reducing compounds containing chromic acid with glucose in absence of free acids other than chromic acid.

4. Process of preparing organic chromium compounds Which consists in reducing salts of chromic acid with glucose.

5. Process of preparing organic chromium compounds which consists in reducing salts of chromic acid with glucose and thiosulfate.

6. Process of preparing organic chromium compounds which consists in reducing compounds containing chromic acid with glucose in absence of free acids different from chromic acid and converting the obtained compounds into soluble chromium salts by the action of acids.

7. Process of preparing organic chromium compounds which consists in reducing salts of chromicacid with glucose and converting the obtained compounds into soluble chromium salts bythe action of acids.

in testimony whereof, I have signed my.

name to this specification in the presence of two subscribing witnesses.

ERNST VGETTER.

Witnesses PAUL Danes, l lnnnr @UADFLZEG. 

